Click here to see the photo gallery. See the full-size gallery Did you know that before the 1940s Thanksgiving was not on a fixed date but was whenever the President proclaimed it to be? George Washington issued the first Presidential proclamation for the holiday in 1789 . That year he designated Thursday, November 26 as a national day of “public thanksgiving.” The United States then celebrated its first Thanksgiving under its new Constitution. Seventy-four years later, in 1863, Abraham Lincoln declared Thanksgiving a national holiday on the last Thursday in November .